Novel insight into antibody diversification from cattle.

The bovine preimmune repertoire develops in the absence of maternal antibodies due to the placental barrier formed by syndesmochorial type of placenta. The limited germline sequence diversity, both at the heavy and light chain loci, imposes constraints on generation of combinatorial diversity in cattle. The cattle, thus, must employ other strategies for antibody diversification. Analysis of VDJ rearrangements in adult cattle have led identification of generation of large IgM antibody molecules that may have an exceptionally long CDR3H region (up to 61 amino acids). The IgM antibodies with an exceptionally long CDR3H are indeed functional as some of these recognize structurally dissimilar antigens. The antibody diversification in cattle involves generation of an exceptionally long CDR3H in addition to point somatic mutations.